Intravenous (IV) infusion therapy is a widespread medical technique in which fluid nutrients or fluid medicaments are infused into the bloodstream of a patient through an IV tube as part of a medical procedure for treatment of the patient. More specifically, an IV administration system for IV infusion includes a fluid source, an IV tube and a venipuncture device inserted through the skin into one of the patient's blood vessels at a venous access site. This establishes a flow path from the fluid source to the blood vessel. The fluid nutrients or medicaments may be pumped from the fluid source through the IV tube or drained by gravity through the IV tube into the patient's bloodstream.
While infusion therapy has proven effective in treating a wide range of maladies, it is not without potential complications. One complication, which is of particular concern, is infiltration of the fluid from the IV set into the patient's tissue. More particularly, it sometimes happens that the medical technician who inserts the needle of the IV tube into the patient may fail to properly insert the needle into a blood vessel and instead the needle is inserted into the tissue which surrounds the blood vessel. This results in the infiltration of the IV fluid into the patient's tissue, rather than passage into the blood vessel.
Infiltration of IV fluid into a patient's tissue can also occur during the course of fluid infusion to a patient even though the IV set was originally established for proper operation. For example, patient motion may cause a needle which was originally properly inserted into a blood vessel to become separated from the vessel or lodge against the wall of the vessel or another obstruction. Moreover, the infusion needle may become clotted or an occlusion may occur in the IV tube upstream of the needle. The following disclosure and claims will be generally couched in terms of an infiltration condition, but the term "infiltration" will be understood to include such conditions as clogging of the needle or occlusion of the tube.
It is unfortunately the case that in many circumstances, infiltration of IV liquids into a patient's tissue can go unnoticed by hospital personnel for relatively lengthy periods. This is because it is not feasible for medical establishments to routinely provide personnel who can continuously monitor each and every IV infusion procedure that the medical establishment undertakes. Such infiltration monitoring procedures are relatively labor intensive and generally require a manual test wherein a venous access device such as a hypodermic syringe needle is placed in fluid communication with the venous access site and a return flow of blood from the vein to the IV tube is initiated.
Such manual techniques are difficult to perform and consequently may be unreliable. As an example, for conducting an infiltration test using a hypodermic syringe, the syringe must first be placed in fluid communication with the IV tube. The tube is then manually pinched while the plunger of the syringe is simultaneously retracted to initiate the return flow of fluid. The absence of blood in the return flow is an indication of infiltration.
This procedure requires a good deal of manual dexterity and experience on the part of the clinician. In addition, due to different syringe sizes and different techniques used for performing an infiltration test, results of the tests may vary. Moreover, relatively high pressures can be generated by the syringe, and these pressures may subject the weakened blood vessel walls to damage and the patient to trauma.
Further, it may often be necessary to infuse a supplemental medicament into the patient during infusion therapy. As an example, the primary infusion may be for maintenance of nutrients, while the supplemental fluid may be an antibiotic, sedative, or a medicament administered in conjunction with chemotherapy. Typically, such a supplemental medicament is administered using the same IV administration set but with a separate hypodermic needle which is connected in flow communication with the IV tube. Using the syringe, the physician or other clinician can infuse a supplemental medicant from the syringe into the patient.
With such a supplemental infusion, as with any other IV administration, it is necessary to monitor for infiltration to ascertain whether the venous access site is patent both before and during the IV infusion of the supplemental medicament. In the past, infiltration has been detected manually by the clinician during the supplemental infusion. Typically this is accomplished by manually pinching or occluding an upstream end of the IV tube and then manipulating the syringe to initiate a return flow of blood from the patient into the IV tube. Often times this procedure must be performed several times during the infusion of the supplemental medicament. Such a procedure, in addition to being difficult to perform, may subject the venous access site to excessive pressures and fluid flow rates. Such high pressures and fluid flow rates may damage the walls of the blood vessel which may be weakened by the venipuncture device.
It is thus desirable to be able to automatically monitor IV infusion procedures to ensure the liquid is being infused into the patient's bloodstream and not into the patient's tissue. Automatic systems for monitoring an infusion procedure for infiltration are known in the art. One such prior art system for automatically detecting infiltration during intravenous infusion is disclosed in U.S. Pat. No. 4,816,019 to Kamen. With this system, a valve is used to close off the IV tube. A piston in fluid communication with the contents of the IV tube is then moved to cause a negative pressure step in the IV tube. If the infusion needle is properly situated in the vein, a quantity of fluid will be drawn into the IV tube and the pressure in the IV tube will return to the pressure prior to the negative pressure step. In an infiltration condition however, the pressure in the IV tube will not return to the pre-step pressure in the same time period. By monitoring the pressure in the IV tube during this procedure an infiltration condition can be detected.
Other infiltration detection systems are also known in the art. Although such automatic infiltration systems may function effectively, there is still some room for improvement in the art. In particular, most of these systems are relatively complicated to operate and may not be portable or easily transported. Others may induce relatively high pressures and flow rates of the medical solution being infused. As previously stated, such high pressures and flow rates may damage the blood vessel and cause patient discomfort. Moreover, the medical solution being infused may be subjected to direct contact and contamination or subjected to excessive agitation by the infiltration detection apparatus. In addition, none of the prior art systems permits an infiltration detection apparatus to be controlled in conjunction with the infusion of a supplemental medical solution into the patient from a secondary source of fluids, such as a syringe.
The present invention is directed to an infiltration detection system which uses relatively low pressures and fluid volumes and in which there is no direct contact with the infusion solution. Additionally, the infiltration detection system of the invention is relatively simple to operate and is reliable and portable. Further, the infiltration detection system of the present invention can be selectively controlled while a hypodermic syringe is used to administer a supplemental medicament. This is accomplished using an infiltration detection apparatus connected to the IV tube of the administration set and a novel pressure sensitive thumb switch which is worn by the clinician to control the infiltration detection apparatus.
Accordingly, it is an object of the present invention to provide a method and apparatus for automatically detecting infiltration during an infusion therapy procedure. Another object of the present invention is to provide a method and apparatus for infiltration detection which requires low fluid pressures and low volumes, and which operates without contacting or substantially agitating the medical solution being infused. It is another object of the present invention to provide a method and apparatus for automatically detecting infiltration during an IV infusion therapy procedure in conjunction with infusion of a supplemental medicament from a hypodermic syringe. It is a further object of the present invention to provide an infiltration detection apparatus having a novel pressure sensitive thumb switch that can be operated in conjunction with a hypodermic syringe coupled to an IV administration set to control the infiltration detection procedure during the infusion of a supplemental medicament. It is yet another object of the present invention to provide an apparatus for infiltration detection that is portable and reliable. Finally it is an object of the present invention to provide a method for infiltration detection that is easy to use and an apparatus that is cost effective to manufacture.